1. Field of the Invention
The subject matter of the present invention pertains to a computer system, and, more particularly, to an apparatus within the computer system which, during an execution of an instruction, stores information which is to be used by subsequent instructions which is related to the results of the execution of the instruction, whereby access to the information is immediately available to the subsequent instructions upon completion of the execution of the instruction.
2. Description of the Prior Art
In a prior art computer system, such as U.S. Pat. No. 4,128,880 to Cray Jr., or U.S. Pat. No. 4,287,566 to Culler, when an instruction is executed, the results of the execution are sometimes stored in a register. Oftentimes, a processor will request certain information related to these results. However, the information must first be generated from the results of the execution of the instruction prior to being passed to the processor. Consequently, time is consumed while generating the information.
For example, assume that the instruction being executed is a COMPARE instruction and that the respective elements of two element strings, referred to as vectors, are being compared to determine whether the magnitude of the first vector element is greater than the magnitude of the respective element of the second vector. An element may be defined as a 32 bit signed binary number, or a floating point short number or a floating point long number. Assume that a third vector, representing the results of the comparison, is stored in the register in the form of a bit string of binary 1s and 0s. The following information is related to the third vector, the results of the comparison, and may be required by the processor during a subsequent instruction execution:
(1) a count of the number of 1s or 0s comprising the bit string representing the third vector stored in the register;
(2) a count of the number of continuous left zeros of the bit string stored in the register;
(3) the addresses of the 1s and 0s comprising the bit string stored in the register.
The processor may complement the third vector and still provide the information recited above. Similarly, the processor may retrieve a bit vector from storage and may perform the logical functions of AND, OR, and EXCLUSIVE OR on the bit vector and the third vector. The processor may retrieve a bit vector from storage and utilize the bit vector as the third vector. The processor may read the third vector and place said vector in storage.
However, in the computer system of the prior art, if, following the execution of the COMPARE instruction, the processor requested one or more of the above items of information, it was necessary to generate this information prior to passing it to the processor.